Which reaction selectively converts an acyl chloride (acid chloride) into an aldehyde using hydrogen gas over a palladium catalyst poisoned with barium sulfate and quinoline?
Answer and explanation
Correct answer: B. Rosenmund reduction
- Step 1: Acyl chlorides can be selectively hydrogenated to aldehydes: .
- Step 2: This transformation is known as the Rosenmund reduction.
- Step 3: The palladium catalyst is deliberately poisoned (moderated) with , sulfur, or quinoline to prevent the aldehyde product from undergoing subsequent over-reduction to a primary alcohol.
Answer
Rosenmund reduction
Why not the others: 'Stephen reaction' reduces nitriles to aldehydes using followed by hydrolysis; 'Clemmensen reduction' reduces carbonyl groups directly to methylene (alkane) using ; 'Etard reaction' oxidizes toluene to benzaldehyde using chromyl chloride ().
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